1. Field of the Invention
The present invention relates generally to rotary bur instruments used for tissue removal and, more specifically, to rotary bur instruments having suction or aspiration passages for removing debris resulting from cutting procedures.
2. Discussion of the Related Art
Surgical cutting instruments in which an elongate inner member is rotated within an elongate, tubular outer member have become well accepted in surgical procedures where access to a surgical site is gained via a narrow portal or passage. Typically, the tubular outer member includes a distal end with an opening, and the inner member includes a distal end with a cutting tip for engaging bodily tissue via the opening. Proximal ends of the inner and outer members commonly include hubs which attach to a handpiece having a motor for rotating the inner member relative to the outer member. The distal end of the inner member can have various configurations dependent upon the cutting procedure to be performed. Often the inner member is tubular so that debris resulting from the cutting procedure can be aspirated through the inner member. It is also common for the direction of rotation of the inner member to be reversible during operation. An example of a rotary tissue cutting instrument of the aforementioned type is described in U.S. Pat. No. 4,203,444 to Bonnell et al for use in performing arthroscopic knee surgery. Other rotary tissue cutting instruments having longitudinal aspiration through the instruments are disclosed in U.S. Pat. Nos. 5,383,884 to Summers, 5,366,468 to Fucci et al, 5,123,904 to Shimomura et al, 5,007,917 to Evans and 4,517,977 to Frost.
The tubular inner and outer members disclosed in the Bonnell et al patent are straight. In many surgical procedures, however, it is desirable for the cutting instruments to be bent, angled or curved to access surgical sites which are generally not accessible with straight cutting instruments. Rotary tissue cutting instruments with curved or bendable shafts are exemplified by U.S. Pat. Nos. 5,922,003 to Anctil et al, 5,322,505 and 5,152,744 to Krause et al, 4,646,738 to Trott, 4,466,429 to Loscher et al and 4,445,509 to Auth.
In the area of head and neck surgery and, in particular, sinus surgery, rotary tissue cutting instruments having burs for the cutting tips have been used for tissue removal, such as removal of bone from a patient's nasal frontal beak. Some rotary bur instruments are angled in that the outer members or shafts thereof have an angle, bend or curve. Prior rotary bur instruments have encountered numerous problems, a primary problem being clogging or jamming of the instruments from debris or tissue buildup. Jamming or clogging of the instruments leads to the need for frequent cleaning or substitution of the instruments during use, which is time consuming thus increasing the duration of the procedure and which contributes to physician fatigue thus increasing the chance of error.
Some rotary bur instruments employed in sinus surgery have aspiration ports proximally of the bur tips for evacuating debris, such as bone, blood and irrigation fluid, via the instruments to deter jamming and clogging. U.S. Pat. No. 5,913,867 to Dion is illustrative of a rotary bur instrument having longitudinally straight inner and outer members or shafts and having an aspiration port proximally of a bur tip. The position of the aspiration ports proximally of the bur tips in prior rotary bur instruments results in aspiration of debris in the immediate vicinity of the aspiration ports while allowing debris to accumulate around and in front of the bur tips. The bur tips are thus difficult to view with endoscopes as typically utilized in sinus procedures.
U.S. Pat. No. 5,759,185 to Grinberg shows a rotary bur instrument having longitudinally straight inner and outer members or shafts and having a bur tip with an interior chamber communicating with a suction passage in the instrument. The interior chamber also communicates with apertures in flutes of the bur tip but does not extend to a distal end of the bur tip. Therefore, suction is not present in front of or at the distal end of the bur tip, giving rise to the problems of debris accumulation and decreased visibility discussed above.
A particular problem of angled rotary bur instruments relates to the external diametric or cross-sectional sizes needed for the angled, curved or bent outer members or shafts to accommodate the structure or components used to enable the inner members or shafts to rotate within the outer members or shafts. The external diametric or cross-sectional sizes of the outer members of prior angled rotary bur instruments are typically larger than desirable, thereby decreasing visibility of the operative site or area by the surgeon and reducing the amount of free area or room available to the surgeon in which to maneuver the angled rotary bur instruments and the endoscopes.
A further problem of prior angled rotary bur instruments is that access to various operative sites or areas is limited by the size of the angles and/or by the locations of the angles, curves or bends in the outer members. The sizes and/or locations for the angles, curves, or bends in prior angled rotary bur instruments is generally dictated by the structure or components used to enable rotation of the inner members within the non-straight outer members. Accordingly, many prior angled rotary bur instruments are unable to meet the needs of surgeons for various angles or ranges of angles for the outer members as well as various locations on the outer members for the angles, bends or curves.